pyramid/cone rocket design specifications

I had always heard the CP was 1/3 of the cones length.

But I'm no authority on it.

Art Upton

Many years ago someone explained CP for odd shape nose cones in a way I coudl easilly understand. Squish the shape down so that it's a cylinder. THe top is the location of the CP.

High school geometry, volume = 1/3 b*h thus the CP of a cone or pyramid is

VERY gray area. I've heard theories on why this works, but nothing proven. I haven't tested yet, but I think it will work withthe top disk smaller than the bottom disk, but not the other way around. It's on my lis tof things to try when I get a "Round Tuit"...

Even more interesting, you can leave off the top plate of the spool, and it still works, but now you've got the CG way forward of the base plate, and the CP is esentially the plate, so it's quite stable.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

This shoold be in the FAQ.

Jerry

"Thermalite is one of those magic and critical substances to rocketry."

- RMR FAQ Part 12 (original versions)

Bob,

You can also leave off the bottom plate, of a spool/spindle, and it still is stable.

At LDRS 21 in Texas, someone flew just such a beast, on a J or K I think. The top plate was painted like a pizza.

Dave Morey

I've got NO clue why that would work!

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

A spool with bottom plate removed is just a cone with the angle at 180 degrees.

A spool with the top plate removed is a cone finned rocket with the angle at 180 degrees.

Thanks for the information. I have decided on the design of my first pyramid rocket. I'm gonna build a full regular icosahedron and have one pyramid "side" shoot off the top.

Ferrell